Unsure that it should be called the Barlow Wadley, as the
invention was by Dr Wadley alone. Who was Barlow? (Not
the Stratford Johns character in Z Cars, that's for sure!)

Is there any reason that the comb has to be harmonics of1MHz? Could it
be 2MHz it the tunable IF were to be 2 - 4 MHz?

Just a thought, with thanks to the anonymous kindly donor of
the 4-gang 500pF tuning condenser if the CLubman type RX
tuned from 1.8 to 5.4 would give as a first attempt, Top
Band, 80 and 60 amateur bands with a reasonably linear tuning
range of 2 - 4 before HF end scale cramping came into play.

/WAFFLE MODE :-)

Gareth's Downstairs Computer
wrote:
Unsure that it should be called the Barlow Wadley, as the
invention was by Dr Wadley alone. Who was Barlow? (Not
the Stratford Johns character in Z Cars, that's for sure!)

Is there any reason that the comb has to be harmonics of1MHz? Could it
be 2MHz it the tunable IF were to be 2 - 4 MHz?

Just a thought, with thanks to the anonymous kindly donor of
the 4-gang 500pF tuning condenser if the CLubman type RX
tuned from 1.8 to 5.4 would give as a first attempt, Top
Band, 80 and 60 amateur bands with a reasonably linear tuning
range of 2 - 4 before HF end scale cramping came into play.

/WAFFLE MODE :-)


Early start on the grog today, then, G? Pace yourself, if you go too mad
too quickly you'll be sick all down yourself by teatime, mate. HTH.

--
STC / M0TEY /
http://twitter.com/ukradioamateur

Gareth's Downstairs Computer wrote:
Unsure that it should be called the Barlow Wadley, as the
invention was by Dr Wadley alone. Who was Barlow? (Not
the Stratford Johns character in Z Cars, that's for sure!)

Barlow was the (south-African) manufacturer who made the Barlow Wadley
XCR-30 portable shortwave receiver, an implementation of the Wadley loop.

Today there is no reason to use this design anymore, as we can make
digital frequency synthesizers and this have a much narrower roofing
filter at 45 MHz or so IF, improving the receiver performance.

Is there any reason that the comb has to be harmonics of1MHz? Could it
be 2MHz it the tunable IF were to be 2 - 4 MHz?

Then the IM performance due to strong signals near the received signal
(inside the first IF range) would be even worse!

On 02/12/2017 16:01, Rob wrote:
Gareth's Downstairs Computer wrote:
Unsure that it should be called the Barlow Wadley, as the
invention was by Dr Wadley alone. Who was Barlow? (Not
the Stratford Johns character in Z Cars, that's for sure!)

Barlow was the (south-African) manufacturer who made the Barlow Wadley
XCR-30 portable shortwave receiver, an implementation of the Wadley loop.

OK, then mea culpa for referring to it previously as the B-W loop.

Today there is no reason to use this design anymore, as we can make
digital frequency synthesizers and this have a much narrower roofing
filter at 45 MHz or so IF, improving the receiver performance.

I go for flywheel-loaded slide rule scales, not yet worked out how
to interface such things with a digital oscillator!

Spinning knobs and flying pointers are much more natural to me than
digits clicking over :-)




Is there any reason that the comb has to be harmonics of1MHz? Could it
be 2MHz it the tunable IF were to be 2 - 4 MHz?

Then the IM performance due to strong signals near the received signal
(inside the first IF range) would be even worse!

If they're near the received signal, then it won't make a lot of
difference as to whether the fitst IF BW is 1MHz or 2MHz!


But thanks for your response, for I see from their (unread) headers that
the Mongolian Hordes of stalking nonces are on my tail, as ever.

Gareth's Downstairs Computer
wrote:
On 02/12/2017 16:01, Rob wrote:
Gareth's Downstairs Computer wrote:
Unsure that it should be called the Barlow Wadley, as the
invention was by Dr Wadley alone. Who was Barlow? (Not
the Stratford Johns character in Z Cars, that's for sure!)

Barlow was the (south-African) manufacturer who made the Barlow Wadley
XCR-30 portable shortwave receiver, an implementation of the Wadley loop.

OK, then mea culpa for referring to it previously as the B-W loop.

Today there is no reason to use this design anymore, as we can make
digital frequency synthesizers and this have a much narrower roofing
filter at 45 MHz or so IF, improving the receiver performance.

I go for flywheel-loaded slide rule scales, not yet worked out how
to interface such things with a digital oscillator!

Spinning knobs and flying pointers are much more natural to me than
digits clicking over :-)




Is there any reason that the comb has to be harmonics of1MHz? Could it
be 2MHz it the tunable IF were to be 2 - 4 MHz?

Then the IM performance due to strong signals near the received signal
(inside the first IF range) would be even worse!

If they're near the received signal, then it won't make a lot of
difference as to whether the fitst IF BW is 1MHz or 2MHz!


But thanks for your response, for I see from their (unread) headers that
the Mongolian Hordes of stalking nonces are on my tail, as ever.


See? I warned you, G, that if you went ape**** on the drink too early you'd
only end up puking yourself. Just make sure you get a couple of pints of
water down your neck so you don't wake up rotten tomorrow, OM.

--
STC / M0TEY /
http://twitter.com/ukradioamateur

Gareth's Downstairs Computer wrote:
On 02/12/2017 16:01, Rob wrote:
Gareth's Downstairs Computer wrote:
Unsure that it should be called the Barlow Wadley, as the
invention was by Dr Wadley alone. Who was Barlow? (Not
the Stratford Johns character in Z Cars, that's for sure!)

Barlow was the (south-African) manufacturer who made the Barlow Wadley
XCR-30 portable shortwave receiver, an implementation of the Wadley loop.

OK, then mea culpa for referring to it previously as the B-W loop.

There are of course other receivers that use the same method, e.g.
the Racal RA14 and the Yaesu FRG-7.

Today there is no reason to use this design anymore, as we can make
digital frequency synthesizers and this have a much narrower roofing
filter at 45 MHz or so IF, improving the receiver performance.

I go for flywheel-loaded slide rule scales, not yet worked out how
to interface such things with a digital oscillator!

Spinning knobs and flying pointers are much more natural to me than
digits clicking over :-)

It is quite common to use shaft encoders to interface a spinning knob
to a microcontroller that sets the frequency of the synthesizer.
Normally a numeric digital readout is used with those, as it is usually
more convenient than a linear scale. However, there is no reason why
you could not mimic a linear scale on a dot-matrix display.

In fact, today usually an SDR is used with a "waterfall" display, that
looks like a linear scale where you can see all nearby transmissions
at the same time and can tune by sliding it to the position you want
to listen to using a spinning knob. But unlike a classic receiver
(without panoramic adapter) you can SEE what you will be tuning to,
making it much more convenient than just blindly tuning around.

On 02/12/2017 16:49, Rob wrote:

There are of course other receivers that use the same method, e.g.
the Racal RA14 and the Yaesu FRG-7.

ITYM RA17? Had one but had no room for it so disposed of it


It is quite common to use shaft encoders to interface a spinning knob
to a microcontroller that sets the frequency of the synthesizer.
Normally a numeric digital readout is used with those, as it is usually
more convenient than a linear scale. However, there is no reason why
you could not mimic a linear scale on a dot-matrix display.

Actually, having retired from a career as electronics engineer and
real-time embedded softy, it would all be well within my capabilty
but I eschew the bus driver's holiday, having considered coupling a
tuning knob to a 4096 gray scale shaft encoder to read the cursor
position, and so I find the 12" slide rule scale with large spiining
knob to be a personably-preferable haptic solution.


In fact, today usually an SDR is used with a "waterfall" display, that
looks like a linear scale where you can see all nearby transmissions
at the same time and can tune by sliding it to the position you want
to listen to using a spinning knob. But unlike a classic receiver
(without panoramic adapter) you can SEE what you will be tuning to,
making it much more convenient than just blindly tuning around.


I prefer some operating skill instead of everything handed on a plate
and also eschew the DX cluster as being a dishonourable technique :-)